This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present techniques. This description is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
The adsorption and removal of contaminants and impurities from gas streams is becoming a significant issue as North America expands the use of its available gas resources, including its natural gas supply. Due to the advances in gas extraction, there is now a sufficient reserve of natural gas to handle much of North America's domestic energy needs for the next century. In fact, the global gas supply is projected to increase about sixty-five percent by 2040, with twenty percent of production occurring in North America.
However, before natural gas is sold commercially as a product, a variety of impurities, including hydrogen sulfide (H2S), carbon dioxide (CO2), heavy hydrocarbons (HHC), water (H2O), mercaptans, and mercury, among other contaminants, must be removed to product specification levels. Such impurities are potentially harmful and can cause undesirable consequences in production equipment and in transportation infrastructure. For example, the H2O and CO2 may freeze at liquefaction temperatures and plug production equipment, and the H2S may decrease the commercial value of the natural gas. Additionally, mercaptans, HHC, and mercury, among other contaminants, are often present in the natural gas in small concentrations. These contaminants may cause possible equipment damage or failure issues, for example, corrosion, metal embrittlement, freezing, and plugging of production equipment.
A conventional gas processing facility for the pre-treatment and production of natural gas production may include a treating vessel, such as a fixed-bed adsorption column, for the removal of contaminants and where the column may be loaded with a solid adsorbent. A suitable solid adsorbent may be selected to adsorb a specific contaminant, where the adsorbent may include, for example, molecular (mole) sieves, silica gel, and activated alumina, among others. Activated carbon is usually used for adsorption of oil and organic solvents, meanwhile silica gel and mole sieves are commonly used for adsorption of water vapor. In operation, the gas stream may enter a top inlet of the fixed-bed adsorption column and flow downward to contact the adsorbent. During the adsorption process, portions of the solid adsorbent may be substantially saturated for hours and, thus, unavailable for active adsorption. Likewise, unused portions of the solid adsorbent may not be utilized for several hours while active saturation takes place in other areas. In both cases, the solid adsorbent is under-utilized.
To desorb and remove the contaminants from the saturated solid adsorbent, a hot regeneration gas may flow through the fixed-bed adsorption column, for example, being introduced through a bottom inlet. However, the flow rate of the regeneration gas through the fixed-bed adsorption column is often limited. For example, an excessive flow rate may cause the mean particle distance of the solid adsorbent to grow, thus, causing the fixed bed to rise. As a result, the solid adsorbent may carry over into a regeneration cooler.
In the oil refinery industry, the fluid catalytic cracking (FCC) process may utilize solid catalysts to increase the speed of reactions and may incorporate regenerators for catalyst regeneration. In particular, the catalyst section of a FCC unit may include two separate vessels, i.e., a reactor and a catalyst regenerator. In operation, a hot vapor and a liquid may be fed into the reactor to fluidize the solid catalysts, which are utilized to increase the rate of reaction. After the reactions take place, the spent catalyst flows into the regenerator for regeneration. As an alternative to fluidization, the reactor of the FCC unit may utilize a moving-bed of solid catalysts that flow downward in the reactor by gravity to increase the rate of reaction.
U.S. Pat. No. 8,500,854 to Pennline et al. describes a carbon dioxide (CO2) adsorption method that uses an amine-based solid sorbent for the removal of CO2 from a gas stream. The method utilizes a conditioner following a steam regeneration process and provides for water loading on the amine-based solid sorbent following CO2 absorption. The method may assist in optimizing the CO2 removal capacity of the amine-based solid sorbent for a given adsorption and regeneration reactor.
U.S. Pat. No. 8,110,523 to Ryu et al. describes a method for preparing a dry regenerable sorbent, which includes the steps of obtaining a slurry through formulation, mixing, comminuting and dispersion of the sorbent raw materials. The method also includes the steps of forming the slurry, spray drying it to produce sorbent particles, then calcining the sorbent particles. In the step of obtaining a slurry, organic additives (e.g., dispersant, a flow control agent, and an organic binder) are used to obtain a well-dispersed, stable and free-flowing slurry in which the raw materials are present below a sub-micron level (e.g., nanosize). The organic additives are removed and decomposed through the calcining. The use of the hydrophilic and high specific surface area support allows the dry regenerable sorbent to have a high reactivity. The solid active component is used instead of a liquid amine. In addition, the sorbent can be re-used through continuous sorption and regeneration processes.
United States Patent Application Publication No. 2012/0192711 by Henningsen et al. describes a fluidized reactor system for removing impurities from a gas. The system includes a fluidized absorber for contacting a feed gas with a sorbent stream to reduce the impurity content of the feed gas and a fluidized solids regenerator for contacting an impurity-loaded sorbent stream with a regeneration gas to reduce the impurity content of the sorbent stream. The system includes a first non-mechanical gas seal forming solids transfer device to receive an impurity-loaded sorbent stream from the absorber, and transport the impurity loaded sorbent stream to the regenerator at a controllable flow rate in response to an aeration gas. The system also includes a second non-mechanical gas seal forming solids transfer device to receive a sorbent stream of reduced impurity content from the regenerator and to transfer the sorbent stream of reduced impurity content to the absorber without changing the flow rate of the sorbent stream.
The removal of contaminants to produce commercial grade natural gas often includes the use of adsorbents to adsorb and remove the contaminants from raw natural gas. After active adsorption of the contaminants, the spent adsorbents may be regenerated to desorb the contaminants and to form regenerated adsorbents for continued use in the adsorption process. Accordingly, there is a need to provide techniques to efficiently utilize and regenerate adsorbent particles.